In the operation switch, if dust and the like adheres to contacts fixed inside a switch case, inferior contacting occurs between the contacts and a moving contact connectable with the former. Therefore, some of recently marketed operation switches have a self-cleaning mechanism to sweep off dust and the like adhered to the contacts.
FIG. 1 illustrates an example of the switch provided with such a self-cleaning mechanism.
In this switch, as an operation member 1 is pushed in the arrow direction, it advances in opposition to the repulsion force of a spring 2. Upon an inner portion of this operation member 1 a slide member 3 is abutting, thus, this slide member 3 also advances at the same time. As a result, a lever 4 abutting upon the slide member 3 pivots about a lower fulcrum 0 provided inside a wafer 5. As the lever 4 pivots, a conductor plate 6 whose upper end is engaged to a bracket 4a provided in rear of the lever 4 is pushed downward in opposition to a tension spring 7. Due to the downward movement of this conductor plate 6 contacts 6a and 8a slide mutually thereby to sweep off dust and the like on respective contacts 6a and 8a (the self-cleaning action). In addition, as shown in FIG. 2 which is a partial enlarged view of FIG. 1, as the operation member 1 is pushed further in the arrow direction, the conductor plate 6 being pushed by the bracket 4a of the lever 4 snaps in the arrow direction owing to the flip-flop action of the tension spring 7, the contact 6a at the tip comes in abuttment with the contact 8a fixed on the other connection terminal 8 (in the alternate long and short dash line position). Then, as the operation member 1 is pushed further, the contact 6a of the conductor plate 6 slides on this contact 8a, whereby the contacts 6a and 8a are self-cleaned (in the alternate long and two short dashes line state). Because the conductor plate 6 is conducted to a connection terminal 9 through the tension spring 7, the circuit of the connection terminal 9 is switched between respective connection terminals 8 in response to operation of the conductor plate 6.
However, the foregoing conventional switch has the following problems:
(1) The number of parts composing the self-cleaning mechanism is many and its manufacturing cost is high.
(2) Because of its complicated structure, its assembling work is troublesome and the number of production steps goes up.